1. Field of the Invention
The present invention relates to a developer container and a developing device of an electrophotographic image forming apparatus, and a process cartridge detachably mountable to an apparatus main body of the electrophotographic image forming apparatus.
2. Description of the Related Art
The electrophotographic image forming apparatus described herein is an apparatus that forms an image on a recording medium by using an electrophotographic image forming process. As the electrophotographic image forming apparatus, there are given, for example, an electrophotographic copying machine, an electrophotographic printer (for example, such as a color laser beam printer and a color LED printer), a facsimile machine, and a word processor.
Further, the process cartridge is detachably mounted onto an electrophotographic image forming apparatus main body (hereinafter, referred to as “apparatus main body”), and contributes to an image forming process for forming an image on a recording medium. In the process cartridge, at least one of a charging means, a developing means, and a cleaning means each serving as a process means and an electrophotographic photosensitive member are integrated into a cartridge, and the thus formed cartridge is detachably mounted to the apparatus main body. The charging means, the developing means, and the cleaning means which act on the electrophotographic photosensitive member (hereinafter, referred to as photosensitive member) are referred to as the process means. The process cartridge may integrally include the developing means and the photosensitive member, and is detachably mounted onto the apparatus main body. The process cartridge may integrally include the charging means, the developing means or the cleaning means, and the photosensitive member, and is detachably mounted onto the apparatus main body. The process cartridge, which integrally includes the photosensitive member and the developing means, is referred to as a so-called integral type. The process cartridge, which integrally includes the photosensitive member and the process means other than the developing means, is referred to as a so-called separation type. The developing cartridge includes a developing roller, and contains a developer (toner) used to develop an electrostatic latent image (hereinafter, referred to as a latent image) formed on the photosensitive member by the developing roller. In a case of the developing cartridge, the photosensitive member is provided to the apparatus main body, a cartridge supporting member, or in the so-called separation type process cartridge (in this case, the process cartridge has no developing means). Here, the developing cartridge and/or the process cartridge can be attached to and detached from the apparatus main body by the user him/herself. Therefore, the user him/herself can easily perform maintenance of the apparatus main body.
(Developing Device)
A dry developing system is used frequently in a developing device. As the dry developing system, there are a two-component developing system using a mixed agent of a toner and a carrier as a developer and a one-component developing system using substantially only a toner. The toner flowability and charging property of a toner are improved by allowing an extraneous additive to adhere to the surface of the toner. In the one-component developing system, a developing device mostly uses a two-chamber configuration of a developer container and a developing chamber. The developer container is filled with a developer (hereinafter, referred to as a toner), and has an agitating member conveying a toner to the developing chamber. The developing chamber has a developer supply member, a developer carrying member, and a developer layer thickness regulating member (hereinafter, referred to as a regulating member). The toner conveyed from the developer container to the developing chamber is allowed to adhere to the developer carrying member by the developer supply member, and is formed into a thin layer and charged by the regulating member. The developer carrying member is supplied with a voltage, and when the toner on the developer carrying member is opposed to an image bearing member, the toner moves to an electrostatic latent image on the image bearing member with an electrostatic force, whereby an electrostatic latent image is developed with toner. Most of the toner that has not been used for development is peeled from the developer carrying member by the developer supply member to be collected into the developing device. The toner in the developing device is thus subjected to friction by the regulating member and the developer supply member. The extraneous additive adhering to the surface of the toner is buried inside the toner or peeled from the toner due to the friction, which degrades the toner. Further, the toner peeled from the developer carrying member mostly has a large particle size. Therefore, as the use of the toner in the developing device proceeds, the particle size distribution changes, and the ratio of the toner with a large particle size increases. The toner flowability and the charging property of the toner in the developing device are degraded gradually.
(Opening of Developer Container and Developing Chamber)
In the case where the developer container and the developing chamber are partitioned with a partition wall having an opening on a plane, a toner moves from the developer container to the developing chamber during use, and the toner also moves from the developing chamber to the developer container. Therefore, the toner that is degraded in the developing chamber and changed in a particle size distribution returns to the developer container. In this case, the toner in the developer container and the developing chamber is degraded as a whole, and hence, toner characteristics are greatly decreased in the later period of the use though the change in toner characteristics is small in the initial period of the use. In order to suppress the decrease in the toner characteristics in the later period of the use, a method of regulating the movement of the toner from the developing chamber to the developer container by the shape of the opening is used. Thus, the toner which is changed in characteristics, and presents in the developing chamber, is used first, and then, the toner in the developer container can keep the initial characteristics even in the later period of the use. As the shape of the opening for regulating the movement of a toner, there is a system for adding an open/close member to the opening (see, for example, Japanese Patent Application Laid-Open No. 2001-331028). Further, there is a partition wall provided with a first partition member extending upward from the bottom of the developing device, and a second partition member disposed on the developing chamber side from the first partition member and extending downward from the upper portion of the developing device. An upper edge portion of the first partition member and a lower edge portion of the second partition member form an opening communicating the developer container with the developing chamber. Then, a system is proposed, which regulates the movement of a toner by appropriately setting the position of the upper edge portion of the first partition member (see Japanese Patent Application Laid-Open No. 2002-049239).
(Toner Seal)
The toner in the developing chamber during use is confined in the developing device by bringing the regulating member and the sealing member around the developer carrying member into contact with the developer carrying member. However, if a toner is placed in the developing chamber before the start of the use, when a shock is applied to the developing chamber during transportation, the regulating member and the sealing member may be vibrated to leave from the developer carrying member. Therefore, there is a possibility that toner leakage may occur. Therefore, the opening provided in the partition wall between the developer container and the developing chamber is covered with a sealing film (a toner seal), thereby sealing the toner in the developer container until the start of the use. In use, a user removes a part of the sealing film to undo the sealing so that the toner can be supplied from the developer container to the developing chamber through the opening. As a system for sealing the opening, the following system is exemplified. A sealing film made of an adhesive layer containing a biaxially-oriented polypropylene layer and an ethylene-vinyl acetate copolymer as main components is attached to the partition wall so as to cover the opening. Then, one end portion of the sealing film is folded to extend to the outside of the developing device (see Japanese Patent No. 3,088,053). In use, a user pulls out the sealing film extending to the outside of the developing device, whereby the adhesive layer of the sealing film is peeled and the sealing film is removed. Thus, the opening is unsealed, and the toner can move from the developer container to the developing chamber. As another system, there is a sealing film mainly made of a biaxially-oriented polypropylene layer with a cut line (ripping line, i.e., tear-off line) formed by a laser along the periphery at which an opening is formed. The sealing film is attached to a wall surface having an opening. Then, one end portion of the sealing film is folded to extend to the outside of the developing device (see Japanese Patent Application Laid-Open No. H08-328369). In use, a user pulls out the sealing film extending to the outside of the developing device, whereby the sealing film is torn apart along the cut line and a part of the sealing film is removed. Thus, the opening is unsealed, and the toner can move from the developer container to the developing chamber. As still another system, the sealing film mainly made of a monoaxially-oriented foamed polypropylene layer is attached to a wall surface having an opening. A flexible film is attached along the surface opposed to the opening of the sealing film. One end portion of the flexible film is folded to extend to the outside of the developing device (see Japanese Patent No. 2,629,945). In use, a user pulls out a flexible film extending to the outside of the developing device, whereby the sealing film is torn apart with substantially the same width as that of the flexible film, and a part of the sealing film is removed. Thus, the developer container is connected to the developing chamber.
In the case of carrying out the method of sealing an opening during transportation on an opening having a configuration in which a change in characteristics of the toner is suppressed by controlling the movement of a developer from the developer container to the developing chamber, there are the following problems.
In the case of using an open/close member for an opening as disclosed in Japanese Patent Application Laid-Open No. 2001-331028, the open/close member has a role of controlling the movement of a developer and a role of sealing the developer container. In order to prevent the leakage of the toner due to the shock during transportation, it is necessary to enhance the stiffness of the open/close member. However, with an open/close member having high stiffness, a toner cannot be supplied from the developer container to the developing chamber at a required speed during use. Therefore, in the case where images with a high coverage rate are printed continuously, there are problems that the density of an image may be degraded or a part of an image may fade to white.
In the case where upper and lower partition walls of the opening are out of alignment as disclosed in Japanese Patent Application Laid-Open No. 2002-049239, it is necessary to seal the developer container by attaching a toner seal to the opening so as to prevent the leakage of a toner during transportation. In this configuration, it is necessary to attach the toner seal to the partition walls being out of alignment, and hence, it is difficult to attach the toner seal.
The conventional toner seal cannot simultaneously satisfy the function of regulating the movement of the toner from the developing chamber to the developer container while supplying the toner from the developer container to the developing chamber at a sufficient speed, and the ease of attachment to the developer container.